This invention relates generally to panel fastener devices of the type which are employed to secure, in a removable manner, a top panel to an underlying panel or support structure, and more particularly to devices of this type which incorporate a screw that is exposed at an access opening in the support structure and adapted to be engaged by an internally threaded fastener stud held captive in a corresponding opening of the panel.
The invention relates more particularly to improvements in the panel fastener illustrated and described in U.S. Pat. No. 3,294,140 dated Dec. 27, 1966, and issued to F. J. Cosenza.
The patented device shows a fastener of the type indicated above, incorporating a housing mounted on a sub-structure or sub-panel, in which there is rigidly carried a screw having a threaded part which projects toward an access opening in the sub-structure, and a floating stud having an internally threaded bore which is captive on an overlying panel, and which can be inserted into the access opening so as to engage the threads of the screw and thereby pull the overlying panel toward the supporting structure. The stud is held captive on the panel by means of a retainer ring having inwardly projecting lugs which are seated in longitudinal grooves in the exterior surface of the stud. The screw is held captive in the housing and is fixed against rotation by means of lugs or tabs 53, as described in column 5, lines 50-53 of the patent. There are two ratchet disks which function to provide a detent action that minimizes the possibility of the stud inadvertently becoming unscrewed under severe operating conditions such as excessive vibration. The ratchet disks are maintained in engagement with one another by a coil spring that bears against the underside of the head of the screw.
While the above construction operated in a generally satisfactory manner as far as withstanding vibration and high temperatures, there existed a distinct drawback in that the studs were susceptible of overtightening by the installer. Also, problems arose with the improper "starting" of the threads during initial engagement of the stud and screw. Under such circumstances, damage to either the stud or screw could occur, rendering the entire assembly inoperative and necessitating replacement of the inoperative parts. Since panels of this type are frequently employed in aircraft, guided missles, etc., where field maintenance is necessary, such replacements caused considerable problems. In addition, in the patented device the screw was firmly held in position in the housing. Where there existed slight misalignments resulting from either manufacturing tolerances or perhaps warping of the panel or the underlying support structure, there could occur difficulty in properly "starting" the threads, if the fastener stud carried by the overlying panel did not properly align with the respective screw. Since no provision was made for enabling the screw to yield or shift position in the housing, even slightly, there was a possibility of binding or seizing of parts. The above considerations constituted serious objections where screw-type fasteners were employed.